Transducers can be employed which utilize optics to provide force or stress measurements. For example, U.S. Pat. No. 4,492,121 to Lehto discloses the use of optics for measuring underwater pressures from explosions. The lehto device employs a piece of ruby, which is bonded to the end of an optical fiber. The ruby is stimulated by a laser to produce a luminescent output. Exposure of the ruby to an underwater explosion allegedly produces a shift in luminescent output frequency as a function of the applied pressure.
Unfortunately, the Lehto device is restricted to measuring isotropic pressures, such as experienced underwater or in other fluid environments. The Lehto device does not allow stress determination under other states of stress, such as uniaxial, biaxial, or complex states involving shear, compressive or tensile stresses in combination.
Accordingly, there remains a need for systems which can reliably produce an indication of stress when subjected to nonisotropic high speed loading with large magnitude stresses.